This invention relates in general to apparatus for electrically inducing ejaculation of animals. More specifically, it relates to a probe that has a self-contained circuitry for automatically generating an output signal waveform of alternating periods of stimulation and rest periods and of varying frequency during each stimulation period across a set of electrodes mounted on the probe.
It is well known that a proper electrical stimulus applied to an animal with a rectal probe will induce ejaculation. Recent studies have demonstrated that electroejaculation is an effective method for producing semen samples of good quality. Such samples are particularly useful in assessing the value of livestock such as bulls and rams for breeding purposes.
In early experiments, a standard 60 cycle household current, suitably reduced in voltage, powered a totally conductive probe. The circuit was completed through a needle electrode inserted in the thigh muscle. Conventional probes in current use are formed of an insulating material and carry multiple external electrodes. The electrical signal is applied across a pair of electrodes typically formed either as closed rings or as longitudinally extending metallic strips or bars.
One problem common to such probes has been that variations in the electrical resistance among individual animals, due for example to the presence of a layer of fecal material between the electrodes and the animal tissue, will cause substantial variations in the power level necessary to induce ejaculation. Unpredictable variations in the required power level occur even when the electrodes are mounted to project above the exterior surface of the probe and thereby displace the fecal layer. As a result, the output signal of conventional commercial electroejaculation devices are controlled manually to achieve ejaculation without injuring the animal by applying excessive power levels. At least a modest degree of skill is required in operating the device.
Another problem common to these probes is that the signal also stimulates motor nerve centers causing uncontrolled kicking, muscle spasms, or discomfort. This problem obviously increases the difficulty of obtaining samples and increases the danger of injury to both the animal and the operator.
The strength and form of the stimulation signal also influence on the effectiveness of the apparatus. While conventional electroejaculation apparatus employ output signals characterized by a wide variety of voltages, currents, frequencies and waveforms (typically a sinusoidal, 60 cycle signal with alternating periods of stimulation and rest), they have operated at a single, fixed frequency, or one of a limited number of fixed frequencies that is selected prior to operation. For example, a study by Watson reported in the Australian Veterinary Journal, Volume 40 (April, 1964) entitled "Field Collection and Evaluation of Semen from Bulls Using Electroejaculation" employed apparatus with a maximum output of 20 volts at 0.5 ampere applied at a frequency of 20 cps. In a more recent article by Furman, Ball and Seidel entitled "Electroejaculation of Bulls Using Pulse Waves of Variable Frequency and Length" appearing in the Journal of Animal Science, Volume 40, No. 4 (1975), sinusoidal stimulation at a frequency of 50 or 80 cps was found to be significantly more effective than the same stimulation at 20 cps. In general, a single frequency may be effective for one species of animals and relatively ineffective for others. Further the response of animals within one species to a selected frequency may vary significantly.
Another difficulty with conventional electroejaculation apparatus is that they require a relatively heavy, cumbersome electrical unit to generate the output signal. For example, the commercially available circuitry used in the Furman experiment (manufactured by the Nicholson Manufacturing Co., a subsidiary of the assignee of the present application) weighs approximately 35 pounds.
This system suffers for several other disadvantages characteristic of conventional electroejaculation apparatus. First, the circuitry has a set of manual controls to select a general power level and to vary manually the voltage output within that level. Manual operation is relatively slow and requires a skilled operator to achieve consistently good results without injury to the animal. Such systems are also susceptible to malfunction due to contamination of the circuitry by dirt, dust and water. In particular, short circuits are a recurring problem since the probe is typically immersed in a conductive solution prior to use.
It is therefore a principal object of this invention to provide an electroejaculation device that is convenient to use and is highly effective for a variety of animals including common livestock and exotic animals.
Another object is to provide an electroejaculation device that is lightweight, compact, fully automatic and induces ejaculation in a significantly shorter time period than conventional apparatus.
Yet another object is to provide an electroejaculation device that is safe for both the animal and the operator.
Still another object of the invention is to provide an electroejaculation device that is resistant to malfunction caused by contaminants.
A further object is to provide an electroejaculation device that has a relatively low power consumption and can be powered by a standard automobile battery.
A still further object of this invention is to provide an electroejaculation device with the foregoing advantages that has a significantly lower cost of manufacture than conventional apparatus of this type.